Loyalty, family service to line of Kim dictators in North Korea has helped top figures avoid purges—or worse

SEOUL—No one is truly safe in Kim Jong Un’s North Korea. But there has long been a degree of security for people whose families faithfully served three generations of Kim dictators, such as that of Choe Ryong Hae, the top official whose recent disappearance has sparked rumors of a purge.

Mr. Choe, considered by many observers to be North Korea’s second or third top official, wasn’t present at this week’s state funeral for a close comrade of North Korea’s founder, Mr. Kim’s grandfather, prompting intense speculation about his...